Update concepts/&str/about.md
Update concepts/&str/about.md

Co-authored-by: Peter Goodspeed-Niklaus <dea3b09e269342fa2efe929fc2dabc7369dca99f@users.noreply.github.com>
exercism/xrust,petertseng/exercism-rust,petertseng/exercism-rust,petertseng/exercism-rust,exercism/xrust